The invention relates to microcontrollers, and more particularly, to a microcontroller having an integral switch mode power supply controller for controlling the charging circuits of a battery charger.
A rechargeable battery requires periodic recharging during its useful life. There are many different types, sizes and capacities of batteries. Each type, size and/or capacity of rechargeable batteries may require a different charging algorithm. The appropriate charging algorithm may be determined by the battery manufacturer. These charging algorithms may be implemented with an intelligent battery charger. The intelligent battery charger may be comprised of a microcontroller, a switch mode power supply (SMPS) controller, a power converter circuit, and a feedback circuit for the battery voltage and/or current (depending on battery type and design requirements).
The microcontroller functions as the intelligence of the charger. Some of the functions performed by the microcontroller are: timing, testing presence of a battery, enabling and controlling the set points to the SMPS controller, performing the battery designer""s proprietary charging algorithm, etc.
The SMPS controller is typically implemented using a general purpose SMPS controller integrated circuit (IC). The SMPS controller IC is designed to generate a constant voltage or constant current to the load. In many lower cost battery chargers, the designer may choose to implement the SMPS controller functions using voltage comparator(s). The SMPS controller module (either the general purpose SMPS controller IC or the simple voltage comparator implementation) may require input(s) to enable/disable the module output, and to change the output voltage/current set points. The SMPS controller module has circuitry to sense signals representing the load (battery) voltage and current, and produces an output signal to drive the power converter circuit. This drive signal is typically in the form of a switched on/off signal, which may employ one of the following techniques: pulse-width modulation, pulse-position modulation, pulse-skipping modulation, etc. The SMPS controller accepts the control signal(s) from the microcontroller, and produces the proper signal/pulses to drive the power converter circuit(s), and makes the attempt to control the feedback voltages (representing the load voltage and/or current of the battery).
The power converter circuit typically comprises discrete power semiconductor devices to handle the high voltage and/or current provided to the load (battery), and a transformer if electrical isolation is required.
The design and implementation of an intelligent battery charger requires multiple integrated circuits (ICs) for the microcontroller, SMPS controller(s), an analog-to-digital converter (ADC), and an analog input multiplexer. The necessity for a plurality of ICs and other discrete components increase the cost, complexity and un-reliability of the intelligent battery charger. What is needed is a more cost effective, simple and reliable system, method and apparatus for designing and implementing the circuitry for an intelligent battery charger.
The invention overcomes the above-identified problems as well as other shortcomings and deficiencies of existing technologies by providing in a single integrated circuit package a battery charger logic and control comprising a microcontroller, a switch mode power supply (SMPS) controller(s), an analog-to-digital converter (ADC) and an analog input multiplexer. The microcontroller, SMPS controller(s), ADC and analog input multiplexer may be fabricated on a single integrated circuit die, or the microcontroller may be on one integrated circuit die, and the remaining aforementioned circuits may be on a second integrated circuit die. Either the single or dual die implementations of the invention may be contained within a single integrated circuit package. This package may be one of the low cost integrated circuit packages for economy to a high reliability package meeting military standards.
For use with lower power batteries, a power converter may be included on the single die or two dice embodiments. Typically for the two dice embodiment, the power converter would be included on the same die as the SMPS controller. Another embodiment of the invention may include a third die comprising high power transistors for the power converter. The single die or two dice embodiments described herein may be packaged with this power transistor die in a high power hybrid integrated circuit package.
In either the single die or two dice embodiments of the invention, the microcontroller reads charge condition value(s) of a battery. The condition value(s) is detected by an analog to digital converter, or if more than one condition value is required, an analog input multiplexer in combination with the analog to digital converter may be used. The analog to digital converter converts the analog condition value(s) of the battery into digital representations of the battery condition value(s) for use by the microcontroller.
The SMPS controller has at least one analog input which is adapted to receive a parameter signal(s) from the power converter. The parameter signal(s) may be battery current and/or voltage, and depending on the charging algorithm, either or both parameter signal(s) may be utilized by the SMPS controller. A setpoint signal(s) is sent to the SMPS controller from the microcontroller. The setpoint signal(s) may change depending on the elapsed charge time, temperature, current, and/or voltage of the battery pursuant to the battery""s charging algorithm. The setpoint signal(s) may be current and/or voltage, and depending on the charging algorithm, either or both may be sent from the microprocessor to the SMPS controller. The SMPS controller has an output which may be a repetition of on/off pulses used to drive the power transistor circuits of a power converter. These on/off pulses may be, for example but not limitation, pulse width, pulse position, or pulse skipping modulation.
Typically, the power converter is made up of discrete semiconductor power devices designed to handle the relatively large voltage and current requirements of the battery. The power converter may include a linear or switching power supply, including an isolation transformer if required, and power transistor(s) to control the amount of voltage and/or current being applied to the battery during its charge cycle. Also contemplated and with the scope of the invention, the power converter may be in the same integrated circuit package as described above.
The SMPS controller in conjunction with the power converter controls the charging profile of the battery according to a battery charging algorithm. The SMPS controller receives the parameter signal(s) (battery current and/or voltage) from the power converter and tries to match this parameter signal(s) to an associated setpoint(s) from the microcontroller. For example in a closed loop charger system, if the parameter signal is representative of the current drawn by the charging battery, then a desired current setpoint from the microcontroller will cause the SMPS controller to increase its pulse output duty cycle when the battery charging current is less than the desired current setpoint value, or to decrease the pulse output duty cycle when the battery charging current is greater than the desired current setpoint value. Voltage to the charging battery may be controlled in the same fashion. Thus the SMPS controller may have a constant voltage (CV) mode, a constant current (CC) mode, or constant voltage with current compliance (CVCC) mode.
The microcontroller in conjunction with the analog to digital converter (ADC) and the analog input multiplexer (if more than one analog input in needed) also may sense condition values from the battery being charged. These condition values may be charging voltage and current, battery temperature, etc. The microcontroller uses these condition values in conjunction with a programmed charging algorithm(s) in determining the setpoint(s) that the microcontroller sends to the SMPS controller.
Embodiments of the invention may include, without limitation thereto: 1) A single battery charger logic and control, comprising: a microcontroller, an analog to digital converter and an SMPS controller adapted for connection to a power converter and charging battery. 2) A multiple battery charger logic and control with sequential or alternating charging of at least two batteries, comprising: a microcontroller, an analog to digital converter, an analog multiplexer and at least two SMPS controllers adapted for connection to a power converter, a power transfer switch and two charging batteries. 3) A multiple battery charger logic and control with simultaneous charging of at least two batteries comprising a microcontroller, an analog to digital converter, an analog multiplexer and at least two SMPS controllers adapted for connection to at least two power converters and at least two charging batteries. Any of the aforementioned combinations, 1)-3), may also include the power converter either on the same die as the SMPS controller or on a separate power transistor die included in a hybrid power integrated circuit package.
A charger logic and control for charging a plurality of batteries having different capacities, voltages, and/or chemistry types are contemplated and within the scope of the invention. The plurality of batteries may be sequentially, alternately and/or simultaneously charged according to the invention. The state of charge of each battery may be independent of the others, and each battery may reach its full charge state independently.
The invention may also calculate the amount of power being used for charging and can limit the maximum power being drawn during charging to a predefined value. The invention is also most advantageous for use in power supplies, un-interruptible power supplies (UPS), CO detectors, and other power related applications where the intelligence of a programmable microcontroller is desired.
Other and further features and advantages will be apparent from the following description of presently preferred embodiments of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings.